/*
 * Copyright (C) 2011 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.hash;

import com.google.common.annotations.Beta;
import com.google.common.base.Preconditions;
import java.io.OutputStream;
import java.io.Serializable;
import java.nio.charset.Charset;
import javax.annotation.Nullable;

/**
 * Funnels for common types. All implementations are serializable.
 *
 * @author Dimitris Andreou
 * @since 11.0
 */
@Beta
public final class Funnels {
    private Funnels() {}

    /**
     * Returns a funnel that extracts the bytes from a {@code byte} array.
     */
    public static Funnel<byte[]> byteArrayFunnel() {
        return ByteArrayFunnel.INSTANCE;
    }

    private enum ByteArrayFunnel implements Funnel<byte[]> {
        INSTANCE;

        public void funnel(byte[] from, PrimitiveSink into) {
            into.putBytes(from);
        }

        @Override
        public String toString() {
            return "Funnels.byteArrayFunnel()";
        }
    }

    /**
     * Returns a funnel that extracts the characters from a {@code CharSequence}, a character at a
     * time, without performing any encoding. If you need to use a specific encoding, use
     * {@link Funnels#stringFunnel(Charset)} instead.
     *
     * @since 15.0 (since 11.0 as {@code Funnels.stringFunnel()}.
     */
    public static Funnel<CharSequence> unencodedCharsFunnel() {
        return UnencodedCharsFunnel.INSTANCE;
    }

    private enum UnencodedCharsFunnel implements Funnel<CharSequence> {
        INSTANCE;

        public void funnel(CharSequence from, PrimitiveSink into) {
            into.putUnencodedChars(from);
        }

        @Override
        public String toString() {
            return "Funnels.unencodedCharsFunnel()";
        }
    }

    /**
     * Returns a funnel that encodes the characters of a {@code CharSequence} with the specified
     * {@code Charset}.
     *
     * @since 15.0
     */
    public static Funnel<CharSequence> stringFunnel(Charset charset) {
        return new StringCharsetFunnel(charset);
    }

    private static class StringCharsetFunnel implements Funnel<CharSequence>, Serializable {
        private final Charset charset;

        StringCharsetFunnel(Charset charset) {
            this.charset = Preconditions.checkNotNull(charset);
        }

        public void funnel(CharSequence from, PrimitiveSink into) {
            into.putString(from, charset);
        }

        @Override
        public String toString() {
            return "Funnels.stringFunnel(" + charset.name() + ")";
        }

        @Override
        public boolean equals(@Nullable Object o) {
            if (o instanceof StringCharsetFunnel) {
                StringCharsetFunnel funnel = (StringCharsetFunnel) o;
                return this.charset.equals(funnel.charset);
            }
            return false;
        }

        @Override
        public int hashCode() {
            return StringCharsetFunnel.class.hashCode() ^ charset.hashCode();
        }

        Object writeReplace() {
            return new SerializedForm(charset);
        }

        private static class SerializedForm implements Serializable {
            private final String charsetCanonicalName;

            SerializedForm(Charset charset) {
                this.charsetCanonicalName = charset.name();
            }

            private Object readResolve() {
                return stringFunnel(Charset.forName(charsetCanonicalName));
            }

            private static final long serialVersionUID = 0;
        }
    }

    /**
     * Returns a funnel for integers.
     *
     * @since 13.0
     */
    public static Funnel<Integer> integerFunnel() {
        return IntegerFunnel.INSTANCE;
    }

    private enum IntegerFunnel implements Funnel<Integer> {
        INSTANCE;

        public void funnel(Integer from, PrimitiveSink into) {
            into.putInt(from);
        }

        @Override
        public String toString() {
            return "Funnels.integerFunnel()";
        }
    }

    /**
     * Returns a funnel that processes an {@code Iterable} by funneling its elements in iteration
     * order with the specified funnel. No separators are added between the elements.
     *
     * @since 15.0
     */
    public static <E> Funnel<Iterable<? extends E>> sequentialFunnel(Funnel<E> elementFunnel) {
        return new SequentialFunnel<E>(elementFunnel);
    }

    private static class SequentialFunnel<E> implements Funnel<Iterable<? extends E>>, Serializable {
        private final Funnel<E> elementFunnel;

        SequentialFunnel(Funnel<E> elementFunnel) {
            this.elementFunnel = Preconditions.checkNotNull(elementFunnel);
        }

        public void funnel(Iterable<? extends E> from, PrimitiveSink into) {
            for (E e : from) {
                elementFunnel.funnel(e, into);
            }
        }

        @Override
        public String toString() {
            return "Funnels.sequentialFunnel(" + elementFunnel + ")";
        }

        @Override
        public boolean equals(@Nullable Object o) {
            if (o instanceof SequentialFunnel) {
                SequentialFunnel<?> funnel = (SequentialFunnel<?>) o;
                return elementFunnel.equals(funnel.elementFunnel);
            }
            return false;
        }

        @Override
        public int hashCode() {
            return SequentialFunnel.class.hashCode() ^ elementFunnel.hashCode();
        }
    }

    /**
     * Returns a funnel for longs.
     *
     * @since 13.0
     */
    public static Funnel<Long> longFunnel() {
        return LongFunnel.INSTANCE;
    }

    private enum LongFunnel implements Funnel<Long> {
        INSTANCE;

        public void funnel(Long from, PrimitiveSink into) {
            into.putLong(from);
        }

        @Override
        public String toString() {
            return "Funnels.longFunnel()";
        }
    }

    /**
     * Wraps a {@code PrimitiveSink} as an {@link OutputStream}, so it is easy to
     * {@link Funnel#funnel funnel} an object to a {@code PrimitiveSink} if there is already a way
     * to write the contents of the object to an {@code OutputStream}.
     *
     * <p>
     * The {@code close} and {@code flush} methods of the returned {@code OutputStream} do nothing,
     * and no method throws {@code IOException}.
     *
     * @since 13.0
     */
    public static OutputStream asOutputStream(PrimitiveSink sink) {
        return new SinkAsStream(sink);
    }

    private static class SinkAsStream extends OutputStream {
        final PrimitiveSink sink;

        SinkAsStream(PrimitiveSink sink) {
            this.sink = Preconditions.checkNotNull(sink);
        }

        @Override
        public void write(int b) {
            sink.putByte((byte) b);
        }

        @Override
        public void write(byte[] bytes) {
            sink.putBytes(bytes);
        }

        @Override
        public void write(byte[] bytes, int off, int len) {
            sink.putBytes(bytes, off, len);
        }

        @Override
        public String toString() {
            return "Funnels.asOutputStream(" + sink + ")";
        }
    }
}
